This has been submitted several times already to HN, with more detailed articles. (A question, how do you dudes find these duplicates?)

tl;dr is that there exists a chamber so quiet that people find it extremely uncomfortable (for various reasons, feel free to speculate), at Orfield Labs. It works simply by reducing echo (anechoic chamber). There will be an award for anyone standing in there for more than 45 minutes. And it's in Guinness Book of Records as the most quiet place on earth.